/*
* Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/**
* @file
*
* GDB stub for remote debugging
*
*/
#include <stdlib.h>
#include <stdint.h>
#include "serial.h"
typedef uint32_t gdbreg_t;
enum {
POSIX_EINVAL = 0x1c, /* used to report bad arguments to GDB */
SIZEOF_PAYLOAD = 256, /* buffer size of GDB payload data */
DR7_CLEAR = 0x00000400, /* disable hardware breakpoints */
DR6_CLEAR = 0xffff0ff0, /* clear breakpoint status */
};
/* The register snapshot, this must be in sync with interrupt handler and the
* GDB protocol. */
enum {
GDBMACH_EAX,
GDBMACH_ECX,
GDBMACH_EDX,
GDBMACH_EBX,
GDBMACH_ESP,
GDBMACH_EBP,
GDBMACH_ESI,
GDBMACH_EDI,
GDBMACH_EIP,
GDBMACH_EFLAGS,
GDBMACH_CS,
GDBMACH_SS,
GDBMACH_DS,
GDBMACH_ES,
GDBMACH_FS,
GDBMACH_GS,
GDBMACH_NREGS,
GDBMACH_SIZEOF_REGS = GDBMACH_NREGS * sizeof(gdbreg_t)
};
/* Breakpoint types */
enum {
GDBMACH_BPMEM,
GDBMACH_BPHW,
GDBMACH_WATCH,
GDBMACH_RWATCH,
GDBMACH_AWATCH,
};
struct gdbstub {
int exit_handler; /* leave interrupt handler */
int signo;
gdbreg_t *regs;
void (*parse) (struct gdbstub * stub, char ch);
uint8_t cksum1;
/* Buffer for payload data when parsing a packet. Once the
* packet has been received, this buffer is used to hold
* the reply payload. */
char buf[SIZEOF_PAYLOAD + 4]; /* $...PAYLOAD...#XX */
char *payload; /* start of payload */
int len; /* length of payload */
};
/** Hardware breakpoint, fields stored in x86 bit pattern form */
struct hwbp {
int type; /* type (1=write watchpoint, 3=access watchpoint) */
unsigned long addr; /* linear address */
size_t len; /* length (0=1-byte, 1=2-byte, 3=4-byte) */
int enabled;
};
static struct hwbp hwbps[4];
static gdbreg_t dr7 = DR7_CLEAR;
static inline void gdbmach_set_pc(gdbreg_t * regs, gdbreg_t pc)
{
regs[GDBMACH_EIP] = pc;
}
static inline void gdbmach_set_single_step(gdbreg_t * regs, int step)
{
regs[GDBMACH_EFLAGS] &= ~(1 << 8); /* Trace Flag (TF) */
regs[GDBMACH_EFLAGS] |= (step << 8);
}
static inline void gdbmach_breakpoint(void)
{
__asm__ __volatile__("int $3\n");
}
static struct hwbp *gdbmach_find_hwbp(int type, unsigned long addr, size_t len)
{
struct hwbp *available = NULL;
unsigned int i;
for (i = 0; i < sizeof hwbps / sizeof hwbps[0]; i++) {
if (hwbps[i].type == type && hwbps[i].addr == addr
&& hwbps[i].len == len) {
return &hwbps[i];
}
if (!hwbps[i].enabled) {
available = &hwbps[i];
}
}
return available;
}
static void gdbmach_commit_hwbp(struct hwbp *bp)
{
int regnum = bp - hwbps;
/* Set breakpoint address */
switch (regnum) {
case 0:
__asm__ __volatile__("movl %0, %%dr0\n": :"r"(bp->addr));
break;
case 1:
__asm__ __volatile__("movl %0, %%dr1\n": :"r"(bp->addr));
break;
case 2:
__asm__ __volatile__("movl %0, %%dr2\n": :"r"(bp->addr));
break;
case 3:
__asm__ __volatile__("movl %0, %%dr3\n": :"r"(bp->addr));
break;
}
/* Set type */
dr7 &= ~(0x3 << (16 + 4 * regnum));
dr7 |= bp->type << (16 + 4 * regnum);
/* Set length */
dr7 &= ~(0x3 << (18 + 4 * regnum));
dr7 |= bp->len << (18 + 4 * regnum);
/* Set/clear local enable bit */
dr7 &= ~(0x3 << 2 * regnum);
dr7 |= bp->enabled << 2 * regnum;
}
int gdbmach_set_breakpoint(int type, unsigned long addr, size_t len, int enable)
{
struct hwbp *bp;
/* Check and convert breakpoint type to x86 type */
switch (type) {
case GDBMACH_WATCH:
type = 0x1;
break;
case GDBMACH_AWATCH:
type = 0x3;
break;
default:
return 0; /* unsupported breakpoint type */
}
/* Only lengths 1, 2, and 4 are supported */
if (len != 2 && len != 4) {
len = 1;
}
len--; /* convert to x86 breakpoint length bit pattern */
/* Set up the breakpoint */
bp = gdbmach_find_hwbp(type, addr, len);
if (!bp) {
return 0; /* ran out of hardware breakpoints */
}
bp->type = type;
bp->addr = addr;
bp->len = len;
bp->enabled = enable;
gdbmach_commit_hwbp(bp);
return 1;
}
static void gdbmach_disable_hwbps(void)
{
/* Store and clear hardware breakpoints */
__asm__ __volatile__("movl %0, %%dr7\n"::"r"(DR7_CLEAR));
}
static void gdbmach_enable_hwbps(void)
{
/* Clear breakpoint status register */
__asm__ __volatile__("movl %0, %%dr6\n"::"r"(DR6_CLEAR));
/* Restore hardware breakpoints */
__asm__ __volatile__("movl %0, %%dr7\n"::"r"(dr7));
}
/* Packet parser states */
static void gdbstub_state_new(struct gdbstub *stub, char ch);
static void gdbstub_state_data(struct gdbstub *stub, char ch);
static void gdbstub_state_cksum1(struct gdbstub *stub, char ch);
static void gdbstub_state_cksum2(struct gdbstub *stub, char ch);
static void gdbstub_state_wait_ack(struct gdbstub *stub, char ch);
static void serial_write(void *buf, size_t len)
{
char *p = buf;
while (len-- > 0)
serial_putc(*p++);
}
static uint8_t gdbstub_from_hex_digit(char ch)
{
if (ch >= '0' && ch <= '9')
return ch - '0';
else if (ch >= 'A' && ch <= 'F')
return ch - 'A' + 0xa;
else
return (ch - 'a' + 0xa) & 0xf;
}
static uint8_t gdbstub_to_hex_digit(uint8_t b)
{
b &= 0xf;
return (b < 0xa ? '0' : 'a' - 0xa) + b;
}
/*
* To make reading/writing device memory atomic, we check for
* 2- or 4-byte aligned operations and handle them specially.
*/
static void gdbstub_from_hex_buf(char *dst, char *src, int lenbytes)
{
if (lenbytes == 2 && ((unsigned long)dst & 0x1) == 0) {
uint16_t i = gdbstub_from_hex_digit(src[2]) << 12 |
gdbstub_from_hex_digit(src[3]) << 8 |
gdbstub_from_hex_digit(src[0]) << 4 |
gdbstub_from_hex_digit(src[1]);
*(uint16_t *) dst = i;
} else if (lenbytes == 4 && ((unsigned long)dst & 0x3) == 0) {
uint32_t i = gdbstub_from_hex_digit(src[6]) << 28 |
gdbstub_from_hex_digit(src[7]) << 24 |
gdbstub_from_hex_digit(src[4]) << 20 |
gdbstub_from_hex_digit(src[5]) << 16 |
gdbstub_from_hex_digit(src[2]) << 12 |
gdbstub_from_hex_digit(src[3]) << 8 |
gdbstub_from_hex_digit(src[0]) << 4 |
gdbstub_from_hex_digit(src[1]);
*(uint32_t *) dst = i;
} else {
while (lenbytes-- > 0) {
*dst++ = gdbstub_from_hex_digit(src[0]) << 4 |
gdbstub_from_hex_digit(src[1]);
src += 2;
}
}
}
static void gdbstub_to_hex_buf(char *dst, char *src, int lenbytes)
{
if (lenbytes == 2 && ((unsigned long)src & 0x1) == 0) {
uint16_t i = *(uint16_t *) src;
dst[0] = gdbstub_to_hex_digit(i >> 4);
dst[1] = gdbstub_to_hex_digit(i);
dst[2] = gdbstub_to_hex_digit(i >> 12);
dst[3] = gdbstub_to_hex_digit(i >> 8);
} else if (lenbytes == 4 && ((unsigned long)src & 0x3) == 0) {
uint32_t i = *(uint32_t *) src;
dst[0] = gdbstub_to_hex_digit(i >> 4);
dst[1] = gdbstub_to_hex_digit(i);
dst[2] = gdbstub_to_hex_digit(i >> 12);
dst[3] = gdbstub_to_hex_digit(i >> 8);
dst[4] = gdbstub_to_hex_digit(i >> 20);
dst[5] = gdbstub_to_hex_digit(i >> 16);
dst[6] = gdbstub_to_hex_digit(i >> 28);
dst[7] = gdbstub_to_hex_digit(i >> 24);
} else {
while (lenbytes-- > 0) {
*dst++ = gdbstub_to_hex_digit(*src >> 4);
*dst++ = gdbstub_to_hex_digit(*src);
src++;
}
}
}
static uint8_t gdbstub_cksum(char *data, int len)
{
uint8_t cksum = 0;
while (len-- > 0) {
cksum += (uint8_t) * data++;
}
return cksum;
}
static void gdbstub_tx_packet(struct gdbstub *stub)
{
uint8_t cksum = gdbstub_cksum(stub->payload, stub->len);
stub->buf[0] = '$';
stub->buf[stub->len + 1] = '#';
stub->buf[stub->len + 2] = gdbstub_to_hex_digit(cksum >> 4);
stub->buf[stub->len + 3] = gdbstub_to_hex_digit(cksum);
serial_write(stub->buf, stub->len + 4);
stub->parse = gdbstub_state_wait_ack;
}
/* GDB commands */
static void gdbstub_send_ok(struct gdbstub *stub)
{
stub->payload[0] = 'O';
stub->payload[1] = 'K';
stub->len = 2;
gdbstub_tx_packet(stub);
}
static void gdbstub_send_num_packet(struct gdbstub *stub, char reply, int num)
{
stub->payload[0] = reply;
stub->payload[1] = gdbstub_to_hex_digit((char)num >> 4);
stub->payload[2] = gdbstub_to_hex_digit((char)num);
stub->len = 3;
gdbstub_tx_packet(stub);
}
/* Format is arg1,arg2,...,argn:data where argn are hex integers and data is not an argument */
static int gdbstub_get_packet_args(struct gdbstub *stub, unsigned long *args,
int nargs, int *stop_idx)
{
int i;
char ch = 0;
int argc = 0;
unsigned long val = 0;
for (i = 1; i < stub->len && argc < nargs; i++) {
ch = stub->payload[i];
if (ch == ':') {
break;
} else if (ch == ',') {
args[argc++] = val;
val = 0;
} else {
val = (val << 4) | gdbstub_from_hex_digit(ch);
}
}
if (stop_idx) {
*stop_idx = i;
}
if (argc < nargs) {
args[argc++] = val;
}
return ((i == stub->len || ch == ':') && argc == nargs);
}
static void gdbstub_send_errno(struct gdbstub *stub, int errno)
{
gdbstub_send_num_packet(stub, 'E', errno);
}
static void gdbstub_report_signal(struct gdbstub *stub)
{
gdbstub_send_num_packet(stub, 'S', stub->signo);
}
static void gdbstub_read_regs(struct gdbstub *stub)
{
gdbstub_to_hex_buf(stub->payload, (char *)stub->regs, GDBMACH_SIZEOF_REGS);
stub->len = GDBMACH_SIZEOF_REGS * 2;
gdbstub_tx_packet(stub);
}
static void gdbstub_write_regs(struct gdbstub *stub)
{
if (stub->len != 1 + GDBMACH_SIZEOF_REGS * 2) {
gdbstub_send_errno(stub, POSIX_EINVAL);
return;
}
gdbstub_from_hex_buf((char *)stub->regs, &stub->payload[1],
GDBMACH_SIZEOF_REGS);
gdbstub_send_ok(stub);
}
static void gdbstub_read_mem(struct gdbstub *stub)
{
unsigned long args[2];
if (!gdbstub_get_packet_args
(stub, args, sizeof args / sizeof args[0], NULL)) {
gdbstub_send_errno(stub, POSIX_EINVAL);
return;
}
args[1] = (args[1] < SIZEOF_PAYLOAD / 2) ? args[1] : SIZEOF_PAYLOAD / 2;
gdbstub_to_hex_buf(stub->payload, (char *)args[0], args[1]);
stub->len = args[1] * 2;
gdbstub_tx_packet(stub);
}
static void gdbstub_write_mem(struct gdbstub *stub)
{
unsigned long args[2];
int colon;
if (!gdbstub_get_packet_args
(stub, args, sizeof args / sizeof args[0], &colon) || colon >= stub->len
|| stub->payload[colon] != ':' || (stub->len - colon - 1) % 2 != 0) {
gdbstub_send_errno(stub, POSIX_EINVAL);
return;
}
gdbstub_from_hex_buf((char *)args[0], &stub->payload[colon + 1],
(stub->len - colon - 1) / 2);
gdbstub_send_ok(stub);
}
static void gdbstub_continue(struct gdbstub *stub, int single_step)
{
gdbreg_t pc;
if (stub->len > 1
&& gdbstub_get_packet_args(stub, (unsigned long *)&pc, 1, NULL)) {
gdbmach_set_pc(stub->regs, pc);
}
gdbmach_set_single_step(stub->regs, single_step);
stub->exit_handler = 1;
/* Reply will be sent when we hit the next breakpoint or interrupt */
}
static void gdbstub_breakpoint(struct gdbstub *stub)
{
unsigned long args[3];
int enable = stub->payload[0] == 'Z' ? 1 : 0;
if (!gdbstub_get_packet_args
(stub, args, sizeof args / sizeof args[0], NULL)) {
gdbstub_send_errno(stub, POSIX_EINVAL);
return;
}
if (gdbmach_set_breakpoint(args[0], args[1], args[2], enable)) {
gdbstub_send_ok(stub);
} else {
/* Not supported */
stub->len = 0;
gdbstub_tx_packet(stub);
}
}
static void gdbstub_rx_packet(struct gdbstub *stub)
{
switch (stub->payload[0]) {
case '?':
gdbstub_report_signal(stub);
break;
case 'g':
gdbstub_read_regs(stub);
break;
case 'G':
gdbstub_write_regs(stub);
break;
case 'm':
gdbstub_read_mem(stub);
break;
case 'M':
gdbstub_write_mem(stub);
break;
case 'c': /* Continue */
case 'k': /* Kill */
case 's': /* Step */
case 'D': /* Detach */
gdbstub_continue(stub, stub->payload[0] == 's');
if (stub->payload[0] == 'D') {
gdbstub_send_ok(stub);
}
break;
case 'Z': /* Insert breakpoint */
case 'z': /* Remove breakpoint */
gdbstub_breakpoint(stub);
break;
default:
stub->len = 0;
gdbstub_tx_packet(stub);
break;
}
}
/* GDB packet parser */
static void gdbstub_state_new(struct gdbstub *stub, char ch)
{
if (ch == '$') {
stub->len = 0;
stub->parse = gdbstub_state_data;
}
}
static void gdbstub_state_data(struct gdbstub *stub, char ch)
{
if (ch == '#') {
stub->parse = gdbstub_state_cksum1;
} else if (ch == '$') {
stub->len = 0; /* retry new packet */
} else {
/* If the length exceeds our buffer, let the checksum fail */
if (stub->len < SIZEOF_PAYLOAD) {
stub->payload[stub->len++] = ch;
}
}
}
static void gdbstub_state_cksum1(struct gdbstub *stub, char ch)
{
stub->cksum1 = gdbstub_from_hex_digit(ch) << 4;
stub->parse = gdbstub_state_cksum2;
}
static void gdbstub_state_cksum2(struct gdbstub *stub, char ch)
{
uint8_t their_cksum;
uint8_t our_cksum;
stub->parse = gdbstub_state_new;
their_cksum = stub->cksum1 + gdbstub_from_hex_digit(ch);
our_cksum = gdbstub_cksum(stub->payload, stub->len);
if (their_cksum == our_cksum) {
serial_write("+", 1);
if (stub->len > 0) {
gdbstub_rx_packet(stub);
}
} else {
serial_write("-", 1);
}
}
static void gdbstub_state_wait_ack(struct gdbstub *stub, char ch)
{
if (ch == '+') {
stub->parse = gdbstub_state_new;
} else {
/* This retransmit is very aggressive but necessary to keep
* in sync with GDB. */
gdbstub_tx_packet(stub);
}
}
void gdbstub_handler(int signo, gdbreg_t * regs)
{
struct gdbstub stub;
gdbmach_disable_hwbps();
stub.parse = gdbstub_state_new;
stub.payload = &stub.buf[1];
stub.signo = signo;
stub.regs = regs;
stub.exit_handler = 0;
gdbstub_report_signal(&stub);
while (!stub.exit_handler)
stub.parse(&stub, serial_getc());
gdbmach_enable_hwbps();
}